This small cavalry fort can be used as a stand-alone outpost or as part of the garrison for your town, and is a 'required building' if you build in The Borders and want to achieve the title of Marcher Lord. As a premium building, it is already fortified, with stones walls, a small tower, and a gatehouse. The walls are about fifteen feet high, with single story, unfortified, buildings inside. It can accommodate two units of troops, but only one Cavalry unit, and an officer.

While the building costs 4570gp in the Borderlands, and 6855gp in the wilderness, you must spend an extra 1000gp to recruit Light Cavalry and Auxiliaries to supply the garrison, or 1250gp if you want Cavalry Archers.

While this small fort, with the full upgrade described below, could form the basis of a Borders holding, it isn't big enough to form the main defensive base for a Wilderness holding. However, Once you have a reasonable sized Wilderness setting, this is ideal for developing a new settlement on your border - and possibly as a home for one of the PCs in the party.

Upgrades

You can add a wall walk and parapet for 640gp, although this does not attract any new troops, unless you build another bunk room (400gp) or the fort is built in a town, so the that new guards can 'live out'. Even so, you will have to buy arms for them separately, unless you also add an armoury (390gp). In that case, the new guards could be upgraded to any sort of Infantry unit, for the appropriate recruiting fee. These new rooms could be built as a second story, over the existing bunks and war room, next to the tower. However, the small fort will never be able to house a second cavalry unit, as there is no room for more animal stalls. This whole upgrade can be purchased as a package for 1500gp, which includes the cost of one unit of Experienced Guard and one unit of (either) Experienced soldiers or skirmishers.

Employing an Officer (Lieutenant) would increase the effectiveness of your troops, giving them all +1 to hit and damage. However, this stops you using the fort as a home, because the officer will want the bedroom for their own use. Cost To be decided